1. Field of the Invention:
This invention pertains to jumper cables which are used between motor vehicles to restore power to a discharged battery and to jump-start the vehicle engine. More particularly, the present invention relates to jumper cables which have an intermediate open circuit device between clamps at the respective ends of the cables.
2. Prior Art:
Jumper cables or battery booster cables comprise a pair of insulated cables with attached connector devices used as a temporary connection to transfer energy from a charged battery to a discharged battery. Because of the millions of motor vehicles which depend upon battery ignition for engine start, the use of jumper cables to boost power on weak batteries is very common. Unfortunately, many of those using jumper cables are not adequately trained in proper safety procedures. As a consequence, many injuries occur to unsuspecting persons who are unaware of the hazard of jump-starting a vehicle. The seriousness of the problem can be appreciated by the fact that approximately 5% of the more than 40,000 people losing their sight annually are the victims of battery-exploding accidents. This does not take into account the untold thousands that suffer minor injuries in unreported accidents.
In 1978 a study entitled Battery Explosion Tests and Labeling DOT HS-803 665 was completed pursuant to a research contract under the Federal Department of Transportation. The study was done by the Society of Automotive Engineers, Inc. in concert with a task force made up of persons from the Society of Automotive Engineers (SAE) Technical Committees on electrical distribution systems, including representatives of manufacturers, government and public users. As part of this study, SAE reviewed and analyzed data regarding reported battery-explosion and related accidents which was provided by the U.S. Consumer Product Safety Commission.
The government sponsored study revealed that "The preponderance of accident and test data indicate that most explosions are caused by the introduction of an ignition source such as a spark or flame from outside the battery. The ignition source must be placed in a flammable zone of venting hydrogen, which occurs within approximately one to two inches of the point of exit of the gas from the battery's ullage space." DOT report, Page 2-13. Upon ignition, the flame propogates into the interior of the battery cell, causing detonation of the contained hydrogen-rich mixture. Battery acid and casement fragments are blown into the face of the unsuspecting victim.
In the typical battery explosion, the igniting shower of sparks is caused by connection of booster cables to the battery terminals. As the circuit is closed by attachment of the terminal, very high currents attempt to bridge the comparatively high resistance area of the contact between the clamp and terminal, causing intense, localized heating. This results in melting and boiling of the mated metallic surfaces, causing white-hot, molten metal particles to be ejected. If these fall into the ignition region of the cells, explosion is likely. This condition of molten sparks is much greater when the booster cables are improperly reversed or cross-connected between two 12-volt batteries, creating an electrical equivalent of a 24-volt, direct short circuit. The commissioned study revealed that 98.6% of the studied battery accidents could be traced to hydrogen gas ignition. Id. Page 2-18.
The subject research contract proposed that a battery booster cable standard be developed that would minimize (i) short circuits, (ii) reverse polarity connections (iii) arcing at the point of connection and (iv) would be suitable for top and side terminal mounts. The project resulted in the following proposed industry standard for booster cables.
a. Conductors and insulation shall be in accordance with SAE Standard J1127 or J1128;
b. The two cables and attached clamps should be of contrasting colors and permanently identified positive and negative.
c. The cable and connectors shall be a minimum of eight feet long, tip to tip.
d. A durable label is to be attached to the cables to provide proper instructions for use, including an instruction that the final connection is to be made to the block of the engine away from the battery.
Although this instructional approach to solving the risk of battery explosion is useful, it does not impose a structural change to the standard jumper cable configuration used for more than fifty (50) years. No structure is added to the cable to enhance or adapt it for proper safety procedures. Obviously this recommendation assumes that education will be adequate to avoid injury. Unfortunately, this approach does not take into account the inclination of the typical consumer to overlook instructions, particularly if they involve numerous steps. Furthermore, it is well known that the normal circumstances requiring use of jumper cables include adverse conditions of cold, rain, snow and darkness. Such situations do not lend themselves to a careful, academic approach to jump-starting a car. In fact, even well trained persons frequently overlook known safety precautions and carelessly connect the booster cables to the wrong terminal.
The need for a structure safety element formed as part of the jumper cables is evident from the following U.S. Pat. Nos.:
4,006,952; Puckett PA0 3,700,834; Schaefer PA0 2,908,827; Hickman PA0 3,942,027; Fima
Each of these patents disclose a jumper cable system which is adapted for service vehicles. Such cables are typically connected by experienced mechanics who understand the risks of battery explosion and work daily with the problem. Nevertheless, the need to isolate the electrical point of contact of clamps from the battery and otherwise ensure proper polarity is promoted for this more knowledgeable class. This fact also rises further question as to the reasonableness of the "educational" approach of the government. The fact that experienced persons could benefit from improved safety features within an improved jumper cable suggests that a layman who makes only occasional use of such cables should also be protected with a safety cable.
Unfortunately, the cable systems disclosed in the referenced patents are too expensive for the typical consumer. The high cost is particularly impractical when consumer use is so infrequent. Balancing the risk of injury versus the high-cost of a safety cable usually leads a consumer to purchase a cheap cable that hopefully will never be used, but will be there if needed. Accordingly, the above mentioned prior art has failed to recognize a need for a consumer safety cable which is inexpensive but which includes means to isolate the possible ignition spark that triggers an explosion.
U.S. Pat. No. 4,163,134 of Budrose discloses various embodiments of a consumer-related jumper cable; however, many of the typical prior art perceptions have been carried forward into this structure. For example, Budrose utilizes an open circuit device in one of the cables to prevent the user from closing the circuit upon direct attachment of the cable clamps to the battery or vehicle. A variety of switching devices is disclosed for interposing within the cable line. These devices do not, however, ensure that the user will make use of their safety, open-circuit feature. For example, an anxious user may disregard checking the open or closed status of the switch before hurridly attaching the clamps. In adverse weather or darkness, the actual switch position may not be easily seen. Furthermore, the cable system of Budrose has incorporated features which likely place the cost of the safety cables out of reach for typical consumer budgets. From a technical point of view, the circuitry of Budrose includes a different switching element which further complicates the use of the jumper cables. This added element requires even further education of the user beyond that proposed by the government study.
U.S. Pat. No. 4,366,430 by Wright discloses another approach to the problem. The Wright patent suggests insertion of a switch in one of the cables for testing voltage levels at the clamps to determine if the cables have been correctly coupled to the respective positive and negative leads of the batteries. Incorrect attachment prevents final closing of the circuit by means of a mechanical or electrical lockout. This structure fails, however, to deal with several of the significant problems that arise with jumper cable use. For example, the Wright structure still develops a small spark at the battery terminals as the final connections are made. This spark arises because the testing circuit draws a small amount of current to determine the relative voltage levels at the terminals. If the hydrogen envelope at the battery reaches the spark, explosion is likely. With the Wright structure, this small spark occurs each time the jumper cables are coupled--whether correctly or incorrectly. Therefore, the risk of explosion remains with every attachment of the Wright cables.
A second problem which occurs with all the prior art cables is inadvertent grounding between vehicles by bumper contact. When the two vehicles are brought together to permit jumper cables to reach the respective batteries, contact may occur at the bumper or any other part of the vehicles which effectively grounds the vehicles. When the first cable is attached between positive terminals, the attending individual may be startled with an unexpected arc and high risk of explosion. With the cars in such grounding contact, the attachment of one cable to the positive terminals closes the circuit, much to the surprise of the attendant. Accordingly, the ability of Wright to permit interchangeable connection of cables between either positive and negative terminals, the existence of other cables which have the continuous cable for the positive connection, create an unknowing risk of explosion with use of only a single cable coupling.
It is clear that the market has yet to find a reasonable solution for the average consumer in the field of jumper cable safety devices. The conventional jumper cable of the past fifty (50) years (without any safety structure) remains the dominant product for the consumer. Likewise, the government proposals offer little hope of change in the adoption of safety practices which would reduce the occurrance of blindness and other injuries resulting from battery explosions. What is needed therefore is a jumper cable which (i) includes an open circuit mechanism, (ii) does not add excessive expense to discourage its purchase and (iii) does not add new safety devices that require further training or education on the part of the user.